Study On Suitability Of Guangdong Mountainous Area’s Soft Rock Weathered Material For Filling Highway Embankment

Guangzhou-Lianzhou Expressway Project(called Guanglian Expressway below)is one of the important diversion channels of Beijing-Hong Kong-Macao National Expressway.A large amount of weathered soft rock will be produced during the excavation of slope and tunnel.If these weathered soft rocks can be used as embankment fillers,not only can construction costs be reduced,but also the local ecological environment can be protected and green development can be formed.The physical and chemical properties of the soft rock weathering material are easily affected by the external conditions.The climate characteristics of high temperature and rainy in Guangdong will degrade the engineering characteristics of soft rock weathering materials.For the two problems,one is that a large number of soft rock weathering materials are difficult to dispose,the other is that the specification is insufficient for the related quality standards of soft rock subgrade filling.Therefore,the thesis selects — — sandstone and argillaceous siltstone — — two weathered soft rocks widely distributed in the mountainous areas of Guangdong as research subjects.Starting from the particle grading,compaction characteristics,hydraulic characteristics and engineering practice of the filler,the suitability of the two types of weathered soft rock materials as embankment fillers in this area are evaluated through indoor tests,numerical simulation analysis and field tests.The main research results are as follows:1.Study on engineering characteristics of soft rock weathering material in Guangdong mountainous areaThrough indoor geotechnical tests,the engineering characteristics of sandstone and argillaceous siltstone weathering materials such as strength,particle size distribution,compression characteristics,load-bearing ratio,compaction characteristics and other engineering characteristics have been studied,and the feasibility of weathered metamorphic soft rock used as embankment fillers has been evaluated.The water stability of the weathered material is analyzed,and the influence of the degree of weathering on the disintegration of the weathered material is studied.The distribution interval and change rule of the particle parameters of the weathered material of sandstone and argillaceous siltstone under the influence of factors such as water immersion and dry-wet cycle are proposed.A method of sand mixing improvement is proposed for the engineering characteristics of sandstone weathering materials,and puts forward the influence of sand mixing on the compaction characteristics of filling materials through comparative tests.2.Numerical analysis of expressway embankment filled with soft rock weathering materialsMidas GTS NX software is used to analyze the deformation characteristics and slope stability of sandstone and argillaceous siltstone weathered materials in embankment construction stage,and silty clay is selected as the control.The results show that the embankment deformation degree of two kinds of soft rock weathered materials is much less than that of silty clay;The relationship between horizontal displacement of embankment toe and filling height of two kinds of soft rock weathering materials is parabolic,and the change of argillaceous siltstone is faster;The variation law of slope shoulder is similar to that of slope toe,but the amplitude is small;The change of slope ratio has little effect on the deformation of soft rock weathered material embankment;When the safety factor of the slope is fixed,the slopes of the two kinds of soft rock weathering materials can be steeper,so as to save filling materials.3.Research on key construction and quality control technology of expressway embankment filled with soft rock weathering materialsThis paper discusses the selection of compaction equipment and filling paving method.Combined with field test,it studies the influence of compaction work,loose paving thickness,rolling pass and rolling speed on the compaction degree of sandstone weathered material.Combined with settlement monitoring,it puts forward the selection of construction equipment,loose paving thickness,rolling times,rolling speed,compaction time and other parameters for on-site filling of sandstone weathered material embankment The key parameters such as compaction quality detection index can provide reference for the construction of soft rock weathered material embankment.